The use of UAVs to conduct surveillance or fly other payload missions in remote and/or hostile environments or under dangerous conditions has significant benefits. The most obvious of these benefits is the avoidance of human exposure to these environments. Other benefits derive from the ability to equip a UAV with data collection instruments and sensors that provide the capability to collect a large quantity of data over a large data collection area or physically dangerous data without human intervention.
The two most common mission scenarios for small UAVs involve a mobile, land-based host platform such as a truck or trailer, for example, and a ship-based host platform including deep water and shallow water vessels. The ship-based mission platforms present the more challenging environments, particularly for capturing an in-flight UAV. Vessel platforms can be highly unstable due to rolling, pitching and yawing and other unpredictable movements of the vessel in choppy water as well as to forward motion. In addition, small, fixed-wing UAVs on the order of 10 to 300 pounds, and nominally about 100 pounds, are highly vulnerable to airwake turbulence from the vessel superstructure and prevailing winds, and the UAV may have to be captured and stabilized within a very limited space on an already crowded deck.
Conventional net-type capture systems and vertical wire systems known in the art suffer from a number of disadvantages. Both capture system approaches are known to induce high probabilities of UAV damage. These types of systems require manned assistance to complete the retrieval process beyond simply snagging the UAV. Both the weight and the wing span of the UAV being captured can significantly impact these types of capture systems. For example, a net system requires a capture area that covers an entire intended capture aperture rather than merely the space directly in front of the approaching UAV. This requirement may significantly intrude on shipboard structures and deck operations. The host ship must be controlled in bearing and speed to effect a quasi-stable target for the UAV to aim at. Attitude and UAV course errors that result in non-perpendicular initial contact with the net can snag a wingtip thus resulting in inertial forces being magnified in proportion to wing length and subsequent wing damage. The risk of damage may be compounded by subsequent buffeting while the UAV is captured within the net and exposed to prevailing or platform velocity-produced winds. Manual extraction of the UAV from the net must be done carefully to avoid entanglement and loss or destruction of the UAV during transition to storage and data download. Conventional net capture systems are not known to have a UAV lockdown mechanism.
Vertical wire capture systems likewise intrude on shipboard structures and deck operations. They also place constraints on the bearing and speed of the ship based capture structure. A UAV being captured by a vertical wire system initially engages the wire at some point along a wing causing the wire, in a glancing manner, to progress down the leading edge of the wingtip where it is snagged by a hook at the end of the wing. This causes the entire UAV to rapidly transition from flying to pinwheeling about the capture wire. Ultimately the UAV's momentum is reduced to zero, whence it hangs in the air, being buffeted by prevailing and relative winds while being manually secured and lowered to the deck.
Furthermore, these types of systems cannot be used to launch the UAV, thus a separate launch system is required. Although a mobile system may address certain of these issues, even small UAVs may generate significant inertial forces during launch acceleration and retrieval deceleration, requiring a platform having inertial stability, at odds with adaptable mobility.
Accordingly, there is a recognized need for a device that has the capability to launch and to capture a small UAV from a moving, unstable host platform. Such a device benefits from being lightweight and robust, highly maneuverable and adaptable to uncontrolled UAV motions and inertial force displacements generated during launch and capture, compact in size and capable of fully automated operation. The need is further recognized for such a device that can consistently, safely launch and retrieve a small UAV.